On a production compound the upper and lower limbs are identical
1 study
The summary today
The only measurement dates from 2015, on a 55-pound round-wheel compound used to calibrate a model. Limb length, wheel radii and position, the resting angle of the limb and the angle of the eccentric were measured separately on the upper and lower parts of the bow, with a ruler, magnified photographs and a protractor, and the author writes that no significant differences emerged; the model, which is symmetrical, uses the average of the two. It is a single bow from a single maker; the paper does not give the separate values or say by what criterion a difference would have counted as significant; and these are all measures of geometry, since the stiffness of the two limbs is not compared. That the two limbs are interchangeable is the premise of almost every compound tuning procedure, and so far it has been checked on that one bow and nothing more. It is a different question from how the two limbs bend at full draw: even with identical parts, a nocking point above the centre of the string loads them slightly differently.
Also phrased as: "identical compound limbs"; "matched limb pair"; "interchangeable limbs"; "upper and lower limb"; "limb manufacturing tolerance"
In practice
It is taken for granted that a compound's limbs leave the factory as a matched pair, interchangeable between top and bottom, and that any difference in behaviour comes from the cams and the tuning.
Evidence
-
2015
For Equipment tests Published later
On a 55-pound round-wheel compound, limb length, wheel radii, eccentricity, the resting angle of the limb and the angle of the eccentric were measured separately on the upper and lower parts: according to the author there are no significant differences, and the model uses the average of the two. The separate values are not given and the stiffness of the two limbs is not compared.
An advanced model of the round-wheel compound bow · M. Tiermas
Status history
- 2015 Reported To calibrate a model of the round-wheel compound, the author measures separately on the upper and lower parts of a 55-pound bow the limb length, the wheel radii and position and the resting angles, and finds no significant differences; in the model, which is symmetrical, he uses the average. These are measures of geometry on a single bow, with no separate values given and no comparison of stiffness: reported, in the sense that on that bow no differences emerged.
Related
Related articles
Research lines
Cite
Campagna, M. (2026). On a production compound the upper and lower limbs are identical (Version 1). In Evidence Registry. Retrieved 16 October 2026, from https://matteocampagna.com/en/registry/equipment/compound-upper-lower-limbs-identical
@misc{campagna2026_compoundflettentisimmetrici,
author = {Campagna, Matteo},
title = {On a production compound the upper and lower limbs are identical},
year = {2026},
howpublished = {Evidence Registry, matteocampagna.com},
url = {https://matteocampagna.com/en/registry/equipment/compound-upper-lower-limbs-identical},
note = {Version 1; accessed 2026-10-16}
}
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